The notable – and ironic – aspect of the case is that the Court’s decision vacating CSAPR leaves in place the Bush-era Clean Air Interstate Rule, or CAIR, which the Court struck down in 2008, in North Carolina v. EPA. Many readers will recall that, after initially simply vacating CAIR, the Court of Appeals was persuaded by all parties that vacatur would wreak havoc with many states’ implementation plans. The Court thus vacated its vacatur, as it were, and left CAIR in place, while EPA developed a replacement rule.

Leaving aside the merits of the decision in EME Homer City Generation, one might wonder what makes the invalid CAIR more valid than the invalid CSAPR. Is it simply judicial inertia? Did the Court ask itself, since CAIR is already in place, why substitute another invalid rule in its place, knowing that CSAPR too would ultimately be replaced by what EPA might just as well give up and call Transport Rule Release 3.0?

Take it as an example of the old saw – Don’t change lame horses in mid-stream.